The accumulation of water under a concrete slab (generally sitting on the inside portion of a concrete footing structure, relative to the concrete foundation walls) of a building can generate major problems to the building structure, without accounting for discomforts the building resident has to deal with. Water under a concrete slab, usually considered as the basement floor of the building, causes a high level (higher than normal comfortable level) of moisture, which might eventually dampen sections of the floor finishing and/or lower regions of walls. Other problems may occur on the concrete foundation itself. This water can get to the concrete slab by infiltration between the foundation walls and the footing.
All these problems are even more present when there is a positive pressure (hydro-pressure) under the slab. Such water can be stagnant and remain under the slab for extensive periods of time, if not permanently, depending on the soil type. Since there is no real access under the slab, there is no efficient way to get rid of the above-mentioned problems associated with the presence of water or moisture, other than breaking the slab to access the soil underneath. Alternatively, some have tried to drain such water by reaching the area from underneath the footing, but this could induce local displacement (collapsing, falling) of the footing, which will generate even more problematic situations to the structure of the building.
Water can also reach the concrete slab from the interface between the foundation walls and the footing supporting the walls, with the concrete of the foundation walls not fully adhering to the footing, thereby leaving some interstices for water to reach the slab. Furthermore, since the concrete is known to be somewhat porous, it is further easy for water often accumulating at the outer periphery of the footing to slowly flow along the unsealed interface and reach the slab sitting on the inner periphery of the footing. Water easily enters the intersection when accumulated onto the top surface of the footing. This is especially the case when the outside top surface of the footing is slightly inclined downwardly towards the foundation wall, which case is much more frequent than one may think (as if the weight of the concrete slab resting on the footing inside the foundation walls, in addition to a movable ground surface under the footing, would be the main reason of this downward and inward inclination of the footing). This inclination of the footing often breaks the key formed along the interface with the foundation walls, thus allowing the water or moisture to infiltrate therethrough and allow for the local raising of the concrete slab under the hydro pressure.
Accordingly, there is a need for an improved device and method for keeping water away from a main concrete slab.